The design of appropriate Si content overcomes the strength-ductility trade-off in dual-phase high entropy alloy

To reduce the stacking fault energy (SFE) of the alloys, silicon (Si) was introduced into Fe 40 Mn 35 Co 20 Cr 5 dual-phase high entropy alloys (HEAs). We propose a novel mechanism supported by first-principles calculations that predicts Si atoms may preferentially substitute Cr atoms, resulting in enhanced lattice distortion and reduced SFE. Experimental results indicate that incorporating 0.2 wt % Si enhances the ductility of the alloy while maintaining its strength through a synergistic effect involving dislocations and phase transformation. Furthermore, in the Si0.2 alloy, the integrity of 9 R structures were preserved, thereby enhancing the transformation-induced plasticity (TRIP) effect and facilitating attainment of an optimal balance between strength and ductility. However, incorporation of 0.1 wt % and 0.3 wt % Si content leads to a decline in ultimate tensile strength due to improper Si content causing grain growth and premature phase transition. Therefore, meticulous selection of an appropriate Si content is crucial for simultaneously enhancing both strength and ductility.